In the field of miniature electronic devices there are miniature capacitors having conductive end terminations that require testing to insure the quality of their electronic capabilities. One type of contactor used to temporarily connect to the conductive ends of the electronic devices for the purpose of electrical measurements includes a contact roller.
The contact roller is made of an electrically conductive metal material that is rotatable on an axis secured to a base plate or framework of the testing machine via spring support. The spring support may vary in length and include springs that continually bias or urge the supports to the maximum lengths. Presently, the contact roller is preloaded to a constant force. As the test plate moves, the spring support urged the roller toward the path surface whereby the roller rolls on and at the same time presses on the surface of the test path. As an electrical component is moved to the test area via a test plate, the roller rolls off the path surface and onto the end of the electronic component. Once the roller is fully pressed into the component, the part is ready for testing. The downward force exerted by the roller on the component during testing is the same predetermined force exerted on the surface of the test pathway as the test plate moves. The required contact force to make a proper test measurement on an electronic component is about 50 grams. However, as the components that are processed get smaller, the resilience of the metal termination of the components diminish to a point where the allowable contact load drops below the required load for stable testing. The maximum allowable force for the smaller electronic components during motion is only about 20 grams. Therefore, additional force placed on a moving electronic component can cause damage to the component.
Another procedure to eliminate damage to the electronic component includes activating the contact roller so that the roller does not touch the surface of the test plate or the electronic component while the test plate is in motion. This procedure requires the contact roller to be retracted from the test plate and component while the test plate is in motion and then extended when the test plate stops and the component is in place for testing.
In this procedure, the contact roller is actuated by a solenoid coil. When the solenoid coil is de-energized, the contact roller is in a raised position above the test plate. Once the test plate stops and an electronic component is in place at the test station for testing, the solenoid coil energizes and lowers the contact roller. The contact roller is preloaded to a 50 gram vertical force on the electronic component to allow for a stable testing environment. The disadvantage of this procedure is that the raising and lowering of the contact roller causes a 5% to 13% decrease in productivity of the testing system.